A variety of unprocessed slabs, including engineered stone slabs or natural stone slabs, must be cut or calibrated to requirements in a manufacturing process. Typically, this is done with multi-head calibrating equipment to grind the slab thickness to a specified thickness. The number of cutting heads is typically between four and twenty-four.
During processing, the slab is placed on a conveyor belt driven by motor. The slab typically passes through each cutting head in sequence. The series of cutting heads is controlled by a central processor or computer processor in order to determine how much surface material is removed per individual cutting head. For example, Chinese patent CN106737069A describes a specific calibrating machine designed for grinding and polishing slabs. Traditionally multi-head calibrating equipment uses set heights for each cutting head, which are not adjusted in real time. Using this method, the amount of surface material removed by each cutting head is determined by the height set of that individual grinder. If a cutting head is set too high, not enough surface material will be removed, lowering efficiency. If a cutting head is set too low, too much material will be removed, and the grinder's motor will be overloaded and trigger a circuit breaker, stopping the entire machine. In the event of an overloaded grinder, typically the conveyor belt speed is reduced, and/or the grinder height is adjusted in order to reduce load on that specific cutting head.
Usually, the final thickness of the slab is determined by the height of the final cutting head.
In conventional methods the initial thickness of the unprocessed slab is determined at entry via gauge or similar measuring device. Each cutting head is then adjusted either manually or by computer processor in order to remove a specified amount of surface material in sequence. The difference between initial thickness and final desired thickness is determined, and each cutting head is set to remove equal amounts of surface material so that no individual cutting head is overloaded.
However, in actual production, the surface of engineered stone slabs is often uneven and has varying thickness throughout the slab, also known as surface roughness. The surface of the slab being processed has peaks and valleys which will cause uneven load on a specific cutting head depending on the area of the slab being calibrated. Since there is more material to be cut at the valleys, energy consumption is higher compared to peaks which have less material to be cut if the traditional methods are followed where the height of each head in sequence is lowered by the same amount.
Due to this, even with a computer processor determining thickness and adjusting the height of each cutting head, maximum production efficiency is difficult to achieve.
In addition, a variety of engineered and natural stone materials including engineered quartz slabs have different densities and hardness even within a slab. A harder material requires more energy and requires more time to remove surface material without overloading the motor. Natural stone also has varying hardness. Softer material requires less energy to process, so the conveyor belt speed may be increased in conventional methods where the difference in height between each cutting head is equal. In actual production it is difficult to set an optimal conveyor belt speed due to these differences in material hardness, roughness and density.
Japanese patent JP2013056392AA discloses a processing device in which a current load value is monitored, and processing stops when the load current exceeds a preset maximum value. Although useful for protecting machinery, this method significantly inhibits production efficiency.
Due to the above described reasons, it is difficult for each individual cutting head to maintain optimal processing efficiency using conventional automatic control methods. Therefore, the entire system will not be working at optimal conditions and full automation.